The method described in JP-B-Hei 7(1995)-10471 (Patent Document 1) is well known as a method for concentric coupling of components made up of a plurality of members. It is described in Patent Document 1 that, in FIG. 1, a tapered hole (valve seat) 10c is formed in the inner bottom of a nozzle body (an outer cylindrical component) 10, provided with an orifice 11, a swirler (an inner cylindrical component) 12 provided with a through-hole 12a is installed inside the nozzle body 10 while securing a clearance therebetween, and the vicinity of a fitting part between the swirler 12 and the nozzle body 10 (a side of the fitting part, adjacent to the swirler 12) is pressed down by a punch 16 in such a way as to cause localized plastic flow while centering of the tapered hole 10c and the through-hole 12a of the swirler 12 is maintained by use of a positioning guide pin 14, thereby causing both the components to undergo concentric plastic coupling by the force of the plastic flow.
Further, the method described in Japanese Patent No. 3931143 (Patent Document 2) is also well known. In Patent Document 2, it is described that, in addition to the method according to Patent Document 1, protrusions 10d are provided on the bottom of the nozzle body 10, and the swirler 12 is caused to interlock with the protrusions 10d to thereby mechanically suppress deviation in the radial direction, so that coaxiality is prevented from undergoing deterioration.